UK expels 23 Russian diplomats over nerve agent attack

The UK Government will expel 23 Russian diplomats follow the poisoning of a former Russian spy and his daughter.

Prime Minister Theresa May made the announcement in parliament overnight after Russia failed to respond to 24-hour deadline for an explanation into the nerve agent attack.

Sergei Skripal and his daughter Yulia were found unconscious in a park in Salisbury more than 10 days ago and remain in a critical condition.

Theresa May has expelled 23 Russian diplomats following the nerve agent attack. (9NEWS) (AAP)Sergei Skripal and his daughter were attacked with nerve agent. (Supplied) (9news)

Ms May said the diplomats have been identified as "undeclared intelligence officers" and have a week to leave the country.

It is the largest expulsion in the UK since the Cold War.

Ms May said British ministers and the royal family would not be attending the football World Cup in Moscow in June and that all high-level bilateral contacts with Russia have been cancelled.

"They have provided no credible explanation to suggest they lost control of their nerve agent, no explanation as to why Russia has an undeclared chemical weapons program in contradiction to international law," Ms May said, adding that the Russian state was "culpable for attempted murder" of the former spy.

A restaurant in Salisbury near where Sergei Skripal and his daughter Yulia were poisoned. (AAP) (AAP)A view through the window into 'The Mill' pub which has been cordoned off by police in Salisbury, Britain. (EPA/AAP) (EPA/AAP)

Related Articles

"Their response demonstrated complete disdain for the gravity of these events. They have treated the use of a military-grade nerve agent in Europe with sarcasm, contempt and defiance.

"We will freeze Russian state assets wherever we have the evidence that they may be used to threaten the life or property of UK nationals or residents."

Russia has responded to the announcement, saying it was "unacceptable"

Police officers stand watch near where a Russian double agent and his daughter were poisoned. (AAP) (AAP)Military in protective clothing prepare to remove vehicles from a car park in Salisbury. (AAP) (AAP)

"We consider this hostile action as totally unacceptable, unjustified and shortsighted," a statement from the Russian Embassy said.

"All the responsibility for the deterioration of the Russia-UK relationship lies with the current political leadership of Britain."

Ms May also said new legislative proposals would be urgently developed to counter any threat from a hostile state.

"This will include the addition of a targeted power to detain those suspected of hostile state activity at the UK border."

The UK called for a UN Security Council meeting over the attempted murder which will be held later on Wednesday (local time).

The United States, European Union and NATO, as well as Australia and New Zealand, have thrown their support behind Britain following the disclosure that the nerve agent used was Novichok, a toxic chemical developed by the Soviet military.

US President Donald Trump told Ms May by telephone that Russia "must provide unambiguous answers regarding how this chemical weapon, developed in Russia, came to be used in the United Kingdom," the White House said.

The White House said Mr Trump and Ms May "agreed on the need for consequences for those who use these heinous weapons in flagrant violation of international norms."